Just wondering if reduction rings will incease the light intensity that hits the reduced area? I guess theoretically it should, but reduction rings weren't a thing way back when I was last doing underwater photography - but I guess we could have bodgered up something from some plumbing fittings if we had thought to.

I’m no scientist but general observation leads me to think, no they don’t. I use reduction rings with Retra strobes and can’t recall ever thinking I need to turn them down.

My own experience, when using a snoot which is not dissimilar, is that more light is needed because of the way the light is blocked by the constrictions of the funnel. The same could be true even of reduction rings.

But like I say, I’m no scientist and perhaps my subjective view is wrong 😜

1 hour ago, TimG said:

I’m no scientist but general observation leads me to think, no they don’t. I use reduction rings with Retra strobes and can’t recall ever thinking I need to turn them down.

My own experience, when using a snoot which is not dissimilar, is that more light is needed because of the way the light is blocked by the constrictions of the funnel. The same could be true even of reduction rings.

But like I say, I’m no scientist and perhaps my subjective view is wrong 😜

I might have to do some testing sometime, and also see if white PVC increases (or has less of a decrease) than black reduction rings.

If there are no optics (lenses etc.) involved it is hard to believe that the reduction rings create photons

Retra has a reflector that fits inside a reduction ring that I recall increases GN by one stop as the light gets concentrated.

Retra UWT

Reflector

The Reflector boosts the light output by +1 F-stop (in water) and narrows the angle of light for more precise light control. The light output is ideal for macro and CFWA photography in manual or TTL m

yup.

Edited August 18Aug 18 by Tom Kline

On 8/16/2026 at 12:09 PM, CCRphoto said:

I might have to do some testing sometime, and also see if white PVC increases (or has less of a decrease) than black reduction rings.

You probably don't want to do that unless the reduction ring is shaped correctly to concentrate the rays. Reduction rings tighten the beam, but if light is reflected off a white surface it tends to diffuse it a bit which spreads the beam.

The reflector looks like it tightens the beam significantly and is relatively tall, the taller it is the tighter the beam. You might not want it that tight for wide angle work. I know I left my reduction rings on shooting grey nurse sharks with a fisheye and it seemed to help quite a bit with backscatter.

Also you are trying to recover light from the edge of the beam, looking at some data for the retra strobe at 120°beam angle the light falloff in this region is 5 f stops. Doing some measurements on my Strobe it looks like the reduction rings restrict you to about a 90-100° beam angle. At 90 degrees the the light fall off is about 2 stops compared to the center and at 100° it 3 fstops. What does that mean there is not that much light in the outer portion of the beam to recover with a reflective inside surface to the reduction ring. - but that light is enough still to illuminate very closeby backscatter, which the reduction rings block so stop it being illuminated.

so the short version of that is it seems to me there's not enough light in this part of the beam to be worth trying to recover at least on my Retras.

5 hours ago, Tom Kline said:

Retra has a reflector that fits inside a reduction ring that I recall increases GN by one stop as the light gets concentrated.

Retra UWT

Reflector

The Reflector boosts the light output by +1 F-stop (in water) and narrows the angle of light for more precise light control. The light output is ideal for macro and CFWA photography in manual or TTL m

yup.

That's exactly what I use when i'm diving for macro. Less power and concentrated light

11 hours ago, Tom Kline said:

Retra has a reflector that fits inside a reduction ring that I recall increases GN by one stop as the light gets concentrated.

Retra UWT

Reflector

The Reflector boosts the light output by +1 F-stop (in water) and narrows the angle of light for more precise light control. The light output is ideal for macro and CFWA photography in manual or TTL m

yup.

Cheers - that might be worth playing with - I will research those!

6 hours ago, Chris Ross said:

You probably don't want to do that unless the reduction ring is shaped correctly to concentrate the rays. Reduction rings tighten the beam, but if light is reflected off a white surface it tends to diffuse it a bit which spreads the beam.

The reflector looks like it tightens the beam significantly and is relatively tall, the taller it is the tighter the beam. You might not want it that tight for wide angle work. I know I left my reduction rings on shooting grey nurse sharks with a fisheye and it seemed to help quite a bit with backscatter.

Also you are trying to recover light from the edge of the beam, looking at some data for the retra strobe at 120°beam angle the light falloff in this region is 5 f stops. Doing some measurements on my Strobe it looks like the reduction rings restrict you to about a 90-100° beam angle. At 90 degrees the the light fall off is about 2 stops compared to the center and at 100° it 3 fstops. What does that mean there is not that much light in the outer portion of the beam to recover with a reflective inside surface to the reduction ring. - but that light is enough still to illuminate very closeby backscatter, which the reduction rings block so stop it being illuminated.

so the short version of that is it seems to me there's not enough light in this part of the beam to be worth trying to recover at least on my Retras.

Interesting - will do some more reading once I've had some sleep!

1 minute ago, CCRphoto said:

Retra has a reflector that fits inside a reduction ring that I recall increases GN by one stop as the light gets concentrated.

Perhaps the reflector being made of polished stainless steel helps?

The reflector is acting kind of like a lens, so that is not a surprise. The material of the reflector probably is not as important as the surface polish/ reflectivity.

I believe that such a reflector causes a lot of uncontrolled stray light, thus preventing the function of the reduction ring of controlled and reduced light emission angle.

But I am happy to be proven wrong. 😁

13 minutes ago, waso said:

I believe that such a reflector causes a lot of uncontrolled stray light, thus preventing the function of the reduction ring of controlled and reduced light emission angle.

But I am happy to be proven wrong. 😁

I didn't notice any uncontrolled stray light..

3 hours ago, bvanant said:

The reflector is acting kind of like a lens, so that is not a surprise. The material of the reflector probably is not as important as the surface polish/ reflectivity.

Month ago I planned to build my own reflectors for my Retras But I had not enough time to continue my project for the moment. I allready bought some painting bomb to obtain some reflecting surface. Like the original Retra reflector but not as heavy as the original and second point with the possibility to change the size of the output

Aluminum tape is durable and creates a decent reflective surface if applied carefully.

1 hour ago, Grantmac said:

Aluminum tape is durable and creates a decent reflective surface if applied carefully.

A dive buddy made a crazy light modifier out of actual mirrors: The Kaleido-Port!

Cool! taking magic light tubes to a whole new level.